Organic dust flames deal with a field of science in which many complicated phenomena like pyrolysis or devolatization of solid particles and combustion of volatile and char particles take place. One-dimensional flame propagation in the cloud of fuel mixture has been analyzed in which flame structure is divided into three zones: preheat zone, reaction zone and post flame zone.It is assumed that particles pyrolyze first to yield a fuel mixture consisting of gaseous and charry fuel. In this research, the effect of char content on pyrolysis process has taken into account and a novel non-linear burning velocity correlation is obtained. Our results are in a reasonable agreement with experimental data.